Rubber dam

Rubber \Rub"ber\, n.
   1. One who, or that which, rubs. Specifically:
      (a) An instrument or thing used in rubbing, polishing, or
          cleaning.
      (b) A coarse file, or the rough part of a file.
      (c) A whetstone; a rubstone.
      (d) An eraser, usually made of caoutchouc or a synthetic
          rubber[4].
      (e) The cushion of an electrical machine.
      (f) One who performs massage, especially in a Turkish
          bath.
      (g) Something that chafes or annoys; hence, something that
          grates on the feelings; a sarcasm; a rub. --Thackeray.
          [1913 Webster]

   2. In some games, as bridge or whist, the odd game, as the
      third or the fifth, which decides the winner when there is
      a tie between the players; as, to play the rubber; also, a
      contest determined by the winning of two out of three
      games; as, to play a rubber of whist. --Beaconsfield. "A
      rubber of cribbage." --Dickens.
      [1913 Webster]

   3. India rubber; caoutchouc; gum elastic; -- also called
      {natural rubber}.
      [1913 Webster +PJC]

   4. Any substance, whether natural or synthetic, resembling
      India rubber with respect to its elasticity[1].
      [PJC]

   5. A low-cut overshoe made of natural or synthetic rubber[4],
      serving to keep the feet and shoes dry when walking in the
      rain or on a wet surface; -- usually used in the plural.
      [1913 Webster]

   6. A {condom}. [Slang]
      [PJC]

   {Antimony rubber}, an elastic durable variety of vulcanized
      caoutchouc of a red color. It contains antimony sulphide
      as an important constituent.

   {Hard rubber}, a kind of vulcanized caoutchouc which nearly
      resembles horn in texture, rigidity, etc.

   {India rubber}, caoutchouc. See {Caoutchouc}.

   {Rubber cloth}, cloth covered with caoutchouc for excluding
      water or moisture.

   {Rubber dam} (Dentistry), a shield of thin sheet rubber
      clasped around a tooth to exclude saliva from the tooth.
      [1913 Webster]